Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 82 near the shore to around 69 above 3000 feet. Southeast winds up to 15 mph shifting to the south in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 70 near the shore to around 60 above 3000 feet. South winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Cloudy with numerous showers. Highs around 80 near the shore to around 66 above 3000 feet. Southwest winds 10 to 15 mph. Chance of rain 70 percent.

South Kaua’i

Today: Mostly cloudy with scattered showers. Highs 78 to 83. Southwest winds up to 15 mph shifting to the south in the afternoon. Chance of rain 40 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 68. Southwest winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Cloudy and breezy. Frequent showers in the morning, then numerous showers in the afternoon. Highs 76 to 81. Southwest winds 10 to 20 mph. Chance of rain 80 percent.

Kaua’i Mountains

Today: Breezy. Mostly cloudy with scattered showers. Highs 73 to 79 in the valleys to around 63 above 4000 feet. South winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Windy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 68 in the valleys to around 58 above 4000 feet. South winds up to 30 mph shifting to the southwest 10 to 30 mph after midnight. Chance of rain 70 percent.

Wednesday: Windy. Cloudy with frequent showers. Highs 69 to 75 in the valleys to around 60 above 4000 feet. Southwest winds up to 30 mph decreasing to up to 20 mph in the afternoon. Chance of rain 90 percent.

North Kaua’i

Today: Breezy. Partly sunny with scattered showers. Highs 73 to 82. South winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 62 to 70. South winds up to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Wednesday: Mostly cloudy. Breezy. Frequent showers in the morning, then numerous showers in the afternoon. Highs 70 to 79. South winds up to 25 mph with gusts to 45 mph shifting to the west up to 15 mph in the afternoon. Chance of rain 90 percent.

East Kaua’i

Today: Breezy. Mostly cloudy with scattered showers. Highs 72 to 82. South winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 63 to 73. Southwest winds 15 to 25 mph with gusts to 45 mph. Chance of rain 70 percent.

Wednesday: Breezy. Cloudy with frequent showers. Highs 69 to 79. Southwest winds up to 25 mph. Chance of rain 90 percent.

Detailed Forecast

Synopsis

The persistent southerly winds are here to stay through early next week as a series of fronts pass through or nearby to the north. Expect the southerly winds to become strong and gusty tonight through Wednesday as the first front approaches and begins to move through. Increasing moisture associated with the front will bring the rain chances up beginning over the western end of the state later today through tonight, then over the eastern end Wednesday as the front begins to stall and weaken. Drier conditions and light winds will follow over the western end of the state Thursday through Friday. Moderate to breezy southwest winds and increasing moisture will return over the weekend as the next cold front approaches.

Discussion

Satellite imagery showed a persistent plume of moisture being drawn northward nearing Kauai due to a broad cyclonic gyre that has setup over the past week across the northern Pacific. Water vapor imagery depicted a shortwave trough located at the Date Line near Midway this morning that is forecast to rotate through the broad upper trough today through midweek. This upper pulse will drive the attendant surface cold front quickly eastward toward the state today, then through the islands Wednesday through Thursday.
Hi-res model guidance reflects this and shows the pressure gradient tightening over the region with strong and gusty southwest winds evolving over the islands tonight through Wednesday. These winds may become strong enough to trigger a wind advisory in later packages today to account for an increasing potential of damaging downsloping winds tonight through Wednesday. In addition to the winds, guidance shows a line of showers developing along and ahead of the front advancing down the island beginning with Kauai and Oahu late tonight through Wednesday, then the eastern end of the state late Wednesday through Thursday. Although significant accumulations are not anticipated, some showers could become locally heavy at times. Drier conditions and light winds will follow over the western end of the state Thursday through Friday, while some rain chances hold over the eastern end where the moisture axis associated with diminishing front stalls.
Moderate to breezy southwest winds and increasing moisture will return over the weekend as the next cold front approaches.

Aviation

A cold front will continue to approach Kauai from the west today. Ahead of the front, expect light to moderate southerly winds to across the state.
Scattered showers may occur over Kauai and Oahu, closest to the aforementioned front, with partly cloudy skies and mainly dry conditions elsewhere along the island chain.
Southerly/southwesterly winds will increase tonight and become breezy to windy by Wednesday.
No AIRMETS are currently in effect.

Marine

The area is along the western periphery of a surface high centered approximately 1,000 miles northeast of the islands. This is maintaining moderate southerlies over the local waters that will persist through the day. A near-stationary front over the northwest offshore waters will be nudged southeast and down the island chain by the eastern passage of a compact gale low later today. This will tighten the gradient west of the front and result in fresh to locally locally strong south southwesterly winds along and west of the boundary as it moves into the central waters Wednesday. Late week moderate southwesterlies will gradually weaken and veer more westerly this weekend as the front washes out in the vicinity of the east waters and high pressure builds in over the state. The next front is forecast to clip the northern waters this weekend. A series of large, generally medium period west to west-northwest (280-310 degree) swells are expected to arrive through the week. As a result, the nearshore waters surrounding Kauai and windward Oahu waters will remain under a Small Craft Advisory (SCA) through tonight for seas building to, or slightly exceeding, 10 feet.
A west-northwest (290-310 degree) swell is forecast to fill in through the afternoon and evening with an anticipated mid to late morning arrival at the far northwest buoys. A similar swell will be arriving Wednesday night through Thursday. A High Surf Advisory (HSA) remains in effect for double to near triple overhead surf along the north-facing shores of Niihau, Kauai and Oahu…at least double overhead surf along the north-facing shores of Molokai, Maui and the west-facing shores of Oahu. Due to the more westerly component to this swell, the west-facing shores of Molokai, Lanai and Big Island will also experience head high to near double overhead HSA- threshold surf heights. This more westerly swell component will allow for some wrap into southwest and south-facing shores and, along with higher wind waves brought on by stronger south to southwest winds, increase surf along more southern exposures.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Wednesday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Lanai Leeward, Maui Central Valley North, Windward Haleakala, Big Island South.
Small Craft Advisory until 6 AM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Oahu Windward Waters.

Data Courtesy of NOAA.gov